| 摘要 |
Spherical, hard mono- or oligodisperse particles of diameter from 0.1 to 100 mu m are prepared by condensation of partially etherified melamine-formaldehyde precondensates which form a clear solution in water in every ratio, in an aqueous solution of a water-soluble polymer which has strongly acid groups and a K value of from 100 to 160, at pH 3 to 6 and at 20 DEG to 100 DEG C., and condensation of the resulting cloudy solution is continued until the precondensate has been consumed, resulting in a dispersion of the particles. The dispersion is neutralized. The particles can be used in the form of the aqueous dispersion or after isolation from the dispersion. The particles are spherical, hard and non-swellable and can be used, for example, as sizes for plastics, polishes, delustrants, extruders and/or as pigment. The process makes it possible to produce particles of predetermined size and size distribution.
|
